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The seinen manga demographic can sometimes be hard to define. While the textbook definition states it is aimed at audiences over the age of 18, sometimes series are labeled as seinen that feel like they are definitely intended for younger readers. In the general eye, seinen is used to describe mature and gritty series that parents shouldn’t ever let their kids read.
The same is tenfold for anime adaptations. Many people are already aware of the most popular dark seinen adaptations, like 1997’s Berserk and Hellsing Ultimatebut there are so many more gems for seinen fans to discover. Some dive deep into the harsh reality of living, while others are gory and blood-splattered nightmares. Here are 10 of the best seinen adaptations for mature audiences to dive into.
1) Orb: On the Movements of the Earth
Unlike many of the other series on this list, Orb: On the Movements of the Earth doesn’t feature crazy, gory action (although it’s certainly bloody at times). Based on the manga by Uoto, the series is set in 15th-century Poland, where the church enforces the notion that the sun and the planets revolve around the Earth.
Anyone who defies the idea is brutally tortured and killed. The series follows several protagonists, who all stumble upon the idea of heliocentrism (the Earth revolving around the sun). Orb is one of the most underrated series in recent years, diving deep into humans’ fight for truth against oppressive religious forces. It’s intricate and mature storytelling at its finest.
2) Parasyte -The Maxim-
Parasyte -The Maxim- is certainly a popular series, but it still gets lost among the big hitters of the seinen demographic, like Berserk and Tokyo Ghoul. Based on the manga by Hitoshi Iwaaki, Parasyte blends dark themes with gross-out body horror to create a truly gruesome series that every anime fan needs to watch at least once.
Parasyte -The Maxim- revolves around teenager Shinichi Izumi and the alien parasite that tries to take over his body. As Izumi resists the creature, the pair must learn to co-exist, but this makes them the target of other parasites who view their synergy as a threat.
3) Pluto
Pluto‘s manga was written by one of the all-time greats of seinen, Naoki Urasawa. The series is heavily inspired by Astro Boybut it puts a more mature, darker, and violent spin on the beloved robot’s story.
Set in a world where robots cannot harm humans, the series follows Gesicht, who is investigating the murders of seven advanced robots and their human allies. But there isn’t a trace of human evidence at the crime scenes.
4) March Comes in Like A Lion
March Comes in Like a Lion might not seem like your typical mature seinen series, with its brighter color palette and more mundane and relaxed-looking characters. But underneath the veneer lies a grounded and emotional story about the realistic hardships of life, loneliness, and mental health.
Based on the manga by Chica Umino, the series follows shogi player, Rei Kiriyama. Rei is about to turn pro, but he has no life outside of the game and feels overwhelmed with his adult job and adult life, despite being a teenager.
5) Rainbow
Rainbow (Nisha Rokubō no Shichinin) is potentially the heaviest series on the list in terms of its topic and themes. The series is the most realistic story on the list because it is based on real, horrific historical events.
Written by George Abe, a former yakuza member turned mangaka, Rainbow follows six young delinquents in the Shōnan Special Reformatory in the 1950s. Despite suffering endless pain, humiliation, and atrocities, the six try to nestle onto any last semblance of hope they can.
6) Monster
We said that Naoki Urasawa is one of the seinen masters, earning his work two spots on this list. Monster is one of the defining seinen manga, and is considered by many to be one of the best murder mystery series ever written.
Monster follows Dr. Kenzou Tenma, an elite surgeon whose career takes a dark turn when he saves the life of a wounded boy. Nine years later, the boy returns as a string of strange murders is taking place across the city, with some of the victims being Tenma’s colleagues.
7) Goblin Slayer
Goblin Slayer borders between a seinen and a shonen story, but its gruesome violence sways heavily towards the former. The series centers around the titular Goblin Slayer, a high-ranking adventurer who disregards the great beasts of the land to only hunt goblins, believing them to be the biggest threat to humans.
Despite its action-filled premise, Goblin Slayer is immensely dark from the get-go. Its debut episode caused great controversy due to its unrelenting and uncensored depiction of what goblins do to captured humans. However, beyond this episode, it takes a comparably less intense tone for those craving a dark fantasy seinen anime adventure.
8) Class
Class is undoubtedly the most underrated series on this list. The anime was written off by many for using 3D animation. But Class used the style to great effect while containing a complex and weaving narrative about life, death, and immortality.
The episoll is to be saved. Class is set in a world where mysterious immortal beings have arrived on Earth. Believing them to be a threat, the Ajin were rounded up by the authorities and were never seen again. The story centers around hard-working teenager Kei Nagai, whose life changes after he’s killed in a car accident, but mysteriously comes back to life, discovering that he is one of the Ajin.
9) Bokurano
Another underrated gem, Bokurano is based on the manga by Mohiro Kitoh. The series evokes the same sense of thematic awe as Neon Genesis Evangelion (thanks in part to its mechs), but Bokurano grounds its story of heroism through its down-to-earth characters, who are all thrown into a terrible situation.
After playing a game where a robot saves the Earth from invading aliens, fifteen children are stunned when the robot appears in real life, and they’re transported to its cockpit as a similar invasion begins. Bokurano asks what it means to be a hero, and the sacrifice that is asked of the teenagers. Warning, Bokurano is a tough watch.
10) Eleven song
The only horror series on the list, Eleven song is based on the manga by Lynn Okamoto. The story is dark, gruesome, incredibly heavy, and incredibly violent. It is also not immune to controversies, and, in fact, is infamous for its edginess and violence to the point of being considered among the most controversial anime of all time.
The series follows Lucy, a Diclonius (a race of evolved humans with short horns and telekinetic powers) girl who has been rejected by the human race and is subject to inhumane experiments by the government. During her mission for revenge, she suffers a brutal head injury that leaves her with a split personality; one a harmless child, and the other a violent killer.
